This proposal is for a continuation of studies on established cultures of fetal hepatocytes and precursor adipocytes from the genetically obese Zucker rat. The objective is to identify any differences between cells from obese and lean rats that might reflect an action of the fa gene which leads to hyperplastic obesity. Cells will be derived from tissues excised from obese and lean rats of varying ages, from fetus to mature adult, placed in culture and assessed for metabolic activity, morphological characteristics at both light and EM levels, and hormonal responsiveness by variety of microscopic, histochemical and biochemical methods.